| Summary of Significant Accounting Policies (Policies) | 6 Months Ended |
| Jun. 30, 2018 |
| Accounting Policies [Abstract] | |
| Basis of Presentation and Consolidation | Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and the requirements of the Securities and Exchange Commission (the “SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s financial information. The results of operations for the three-month and six-month periods ended June 30, 2018 are not necessarily indicative of the results to be expected for the full year or any other future period. The balance sheet as of December 31, 2017 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. Intercompany accounts and transactions have been eliminated upon consolidation. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K. |
| Liquidity And Going Concern | Liquidity and Going Concern On April 7, 2015, the Company entered into a Common Stock Sales Agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”), pursuant to which the Company could issue and sell shares of our common stock having aggregate sales proceeds of up to $30.0 million from time to time through an at-the-market (“ATM”) equity offering program under which Cowen acted as sales agent. During the six-month period ended June 30, 2018, the Company sold 2,144,454 shares of common stock under the Sales Agreement, at a weighted-average price of approximately $11.51 per share for aggregate gross proceeds of $24.7 million and aggregate net proceeds of $24.0 million, of which all sales took place during the three-month period ended March 31, 2018. As of June 30, 2018, the Company had sold 3,250,003 shares of common stock under the Sales Agreement for aggregate gross proceeds of $30.0 million and aggregate net proceeds of $29.2 million. No shares remain available for sale under the Sales Agreement. On May 31, 2017, the Company completed an underwritten public offering of 5,750,000 shares of its common stock at a price to the public of $22.50 per share, including the closing of the full exercise of the underwriters’ option to purchase an additional 750,000 shares of common stock on June 9, 2017. The Company received net proceeds from the offering of $121.2 million, after deducting the underwriting discounts and commissions and offering expenses. On May 4, 2017, the Company entered into an agreement with the Bill & Melinda Gates Foundation (the “Gates Foundation”) to discover drug candidates against gram-negative bacterial pathogens intended to prevent neonatal sepsis (the “Grant Agreement”). Pursuant to the Grant Agreement, the Gates Foundation awarded the Company up to approximately $10.5 million in grant funding (“Grant Funds”) over a three-year research term, of which approximately $3.2 million was received in May 2017 (the “Advance Funds”). Concurrently with the Grant Agreement, the Company entered into a Common Stock Purchase Agreement (the “Gates Purchase Agreement”) with the Gates Foundation, pursuant to which the Company agreed to sell 407,331 shares of its contingently redeemable common stock to the Gates Foundation in a private placement at a purchase price per share equal to $24.55, for gross proceeds to the Company of $10.0 million (“Gates Investment”). In connection with the Grant Agreement and the Gates Investment, the Company entered into a strategic relationship with the Gates Foundation (the “Letter Agreement”). Under the terms of the Letter Agreement, the Gates Investment and Grant Funds may only be used to conduct mutually agreed upon work, including the scale up of the Company’s antibody platform technology to launch a product intended to prevent neonatal sepsis (the “NSP”). Pursuant to the Letter Agreement, the Company agreed to make the NSP available and accessible in certain developing countries and to grant the Gates Foundation a non-exclusive license to commercialize selected drug candidates in certain developing countries, which may only be exercised in the event of certain defaults as described in the Letter Agreement (the “Global Access Commitments”). The Global Access Commitments will continue in effect until the earlier of 25 years from the closing of the Gates Investment or 7 years following the termination of all funding provided by the Gates Foundation; provided, that the Global Access Commitments will continue for any products or services developed with funding provided by the Gates Foundation which continue to be developed or available in certain developing countries. In September 2017, the Company was awarded a contract (the “C-Scape Contract”) valued at up to $18.0 million in grant funding from the Biomedical Advanced Research and Development Authority (“BARDA”) to support the development of C-Scape. The C-Scape Contract includes a base period with committed funding of $12.0 million and subsequent option periods that, if exercised, would bring the total value of the award to $18.0 million. On February 26, 2018, the Company entered into a new loan and security agreement with Silicon Valley Bank (“SVB”), pursuant to which SVB agreed to make available to the Company term loans with an aggregate principal amount of up to $50.0 million, $20.9 million of which was used to repay our loan with Solar Capital Ltd., $4.1 million of which was provided to us on February 26, 2018 and $25.0 million of which remains available for borrowing until February 26, 2019. On February 27, 2018, the Company filed an amended Registration Statement on Form S-3 (the “2018 Shelf Registration Statement”) covering the offering of up to $250.0 million of common stock, preferred stock, debt securities, warrants and units. In addition, on February 27, 2018, the Company filed a prospectus supplement to the 2018 Shelf Registration Statement covering the offering, issuance and sale of up to $50.0 million shares of the Company’s common stock in ATM offerings pursuant to a Common Stock Sales Agreement entered into with Cowen and Company, LLC (the “2018 Sales Agreement”). On April 24, 2018, the Company was awarded $2.4 million, with a possibility of up to $9.6 million in additional funding based on achievement of certain project milestones, from CARB-X. The funding was awarded to support the development of a next-generation broad-spectrum aminoglycoside antibiotic capable of overcoming clinically-relevant resistance mechanisms and potentially treating highly-resistant gram-negative pathogens such as the Enterobacteriaceae family, Acinetobacter baumannii, and Pseudomonas aeruginosa. The Company has incurred losses and negative cash flows from operations every year since its inception. As of June 30, 2018, the Company had unrestricted cash, cash equivalents and short-term investments of approximately $100.5 million and an accumulated deficit of approximately $470.0 million. Based on the Company’s available cash resources, the Company does not have sufficient funds to support current operations for at least the next twelve months from the filing of this report on Form 10-Q. This condition results in the assessment that there is substantial doubt about the Company’s ability to continue as a going concern. The Company’s plan to address this condition includes seeking additional funds through equity or debt financings, government contracts, third party collaborations, commercial sales of ZEMDRI or other sources to permit additional investments in the commercialization of ZEMDRI and continued research and development efforts. The Company may be unable to obtain equity or debt financings, government contracts, third party collaborations or other sources of additional investment and, if necessary, the Company will be required to implement further cost reduction strategies, including a reduction in the scope of our research and development programs and other operations. The accompanying financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The financial statements do not reflect any adjustments relating to the recoverability and reclassification of assets and liabilities that might be necessary if the Company is unable to continue as a going concern. As of June 30, 2018, the Company had not generated any product revenues and has financed its operations primarily through public offerings and private placements of its equity securities, debt financings and government contracts. There can be no assurance that the Company will be able to obtain additional debt or equity financing or generate product revenue or revenues from collaborative partners, on terms acceptable to the Company, on a timely basis or at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed would adversely affect the Company’s business, results of operations, and financial condition. |
| Use of Estimates | Use of Estimates The accompanying financial statements have been prepared in accordance with U.S. GAAP. The preparation of financial statements in conformity with U.S. GAAP requires management to make judgments, assumptions and estimates that affect the reported amounts of assets, liabilities, revenues and expenses and related disclosures of contingent liabilities. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of derivative and warrant liabilities, common stock and stock-based awards and income taxes. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates. |
| Fair Value of Financial Instruments | Fair Value of Financial Instruments The carrying amounts of the Company’s financial instruments, including cash and cash equivalents, contracts receivable, prepaid and other current assets, accounts payable, accrued liabilities, and other current liabilities approximate fair value due to their short-term maturities. Short-term investments consist of available-for-sale securities and are carried at fair value. Based upon the borrowing rates currently available to the Company for loans with similar terms, the Company believes the carrying amount of the loan payable approximates its fair value. The warrant and derivative liabilities are recorded at estimated fair value with changes in estimated fair value recorded in the Company's statements of operations. |
| Cash and Cash Equivalents | Cash and Cash Equivalents Cash equivalents include only securities having a maturity of three months or less at the time of purchase. As of June 30, 2018 and December 31, 2017, cash and cash equivalents consisted of bank deposits, cash, commercial paper, money market funds, cash repurchase agreement investments and overnight cash sweep investments in government money market funds. |
| Short-term Investments | Short-term Investments Short-term investments consist of debt securities with maturities greater than three months, but less than one year from the date of acquisition, and are classified as available for sale. Short-term investments are carried at fair value. Unrealized gains and losses on available-for-sale securities are excluded from earnings and reported as a component of net unrealized (loss) on available-for-sale securities in the Company's consolidated statements of comprehensive loss. The amortized cost of debt securities reflects amortization of purchase premiums and accretion of purchase discounts to date, which are included in interest income. The Company reviews all of its marketable securities on a regular basis to evaluate whether any security has experienced an other-than-temporary decline in fair value. |
| Restricted Cash | Restricted Cash At June 30, 2018 and December 31, 2017, the Company had restricted cash of $7.0 million and $9.7 million, respectively. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in thousands):
June 30, 2018
December 31, 2017
Cash and cash equivalents
$
63,291
$
145,219
Restricted cash, current
5,757
5,891
Restricted cash, non-current
1,206
3,855
Total cash, cash equivalents, and restricted cash
$
70,254
$
154,965
In May 2017, the Company received $13.2 million of funding from the Gates Foundation from the Grant Funds and Gates Investment (see Note 1). The Letter Agreement restricts the Company’s use to expenditures that are reasonably attributable to the activities required to support the research projects funded by the Gates Foundation, including an allocation of overhead and administrative expenses. As of June 30, 2018 and December 31, 2017, the Company had $6.4 million and $9.2 million, respectively, of restricted cash related to the cash provided by the Gates Foundation. As of June 30, 2018 and December 31, 2017, the Company had $0.5 million of restricted cash, which relates to the Company’s facility leases. |
| Segment Reporting | Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker regarding resource allocation and assessing performance. The Company has one operating segment. |
| Customer Concentration | Customer Concentration For the three-month and six-month periods ended June 30, 2018 and 2017, the Company’s revenue was generated from funding pursuant to U.S. government contracts and a non-profit foundation grant. All contracts receivable relate to funding from U.S. government contracts. |
| Concentration of Credit Risk | Concentration of Credit Risk Financial instruments that potentially subject the Company to a significant concentration of credit risk consist of cash, cash equivalents and short-term investments. Cash and cash equivalents are deposited in checking, overnight sweep and money market accounts at one financial institution with balances that generally exceed federally insured limits. Management believes that the financial institution is financially sound, and, accordingly, minimal credit risk exists with respect to this financial institution. The Company’s investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of default by the institutions holding its cash and cash equivalents or issuing the debt securities. As of June 30, 2018 and December 31, 2017, the Company had not experienced any credit losses in such accounts or investments. |
| Revenue Recognition | Revenue Recognition The Company evaluated Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers Funds received from third parties under contract or grant arrangements are recorded as revenue if the Company is deemed to be the principal participant in the arrangements because the activities under the contracts or grants are part of the Company’s development programs. If the Company is not the principal participant, the funds from contracts or grants are recorded as a reduction to research and development expense. Contract funds received are not refundable and are recognized when the related qualified research and development costs are incurred and there is reasonable assurance that the funds will be received. Funds received in advance are recorded as deferred revenue. Management has determined that the Company is the principal participant under the Company’s government contract arrangements and non-profit grant agreement, and accordingly, the Company records amounts earned under these arrangements as revenue. |
| Research and Development Costs | Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses include certain payroll and personnel expenses, laboratory supplies, consulting costs, external contract research and development expenses, and allocated overhead, including rent, equipment depreciation, and utilities and relate to both Company-sponsored programs as well as costs incurred pursuant to collaboration agreements, non-profit grants and government contracts. Nonrefundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and recognized as an expense as the goods are delivered or the related services are performed. For certain research and development services where the Company has not yet been invoiced or otherwise notified of actual cost from the third-party contracted service providers, the Company is required to estimate the extent of the services that have been performed on the Company’s behalf and the associated costs incurred at each reporting period. The majority of the service providers invoice the Company monthly in arrears for services performed. The Company makes estimates of the accrued expenses as of each balance sheet date in the consolidated financial statements based on facts and circumstances known to the Company at that time. The Company periodically confirms the accuracy of the estimates with the service providers and makes adjustments if necessary. Examples of estimated accrued research and development expenses include services from:
•
contract research organizations (“CROs”) and other service providers in connection with clinical studies;
•
contract manufacturers in connection with the production of clinical trial materials; and
•
vendors in connection with preclinical development activities. The Company bases the expenses related to preclinical studies and clinical trials on estimates of the services received and efforts expended pursuant to contracts with multiple research institutions and CROs that conduct and manage such studies and trials on the Company’s behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows and expense recognition. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In accruing service fees, the Company estimates the time period over which these services will be performed and the level of effort to be expended and costs to be incurred during each reporting period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company adjusts the accrual accordingly. The Company’s estimation of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting changes in estimates in any particular period. To date, there have been no material adjustments from the Company’s estimates to the amount actually incurred. |
| Property and Equipment, Net | Property and Equipment, Net Property and equipment consist of office equipment, laboratory equipment, and leasehold improvements and are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the respective assets, generally three to seven years. Leasehold improvements are amortized over their estimated useful lives or the remaining lease term, whichever is shorter. Maintenance and repair costs are recorded as a component of operating expenses in the Company’s consolidated statement of operations when incurred. |
| Impairment of Long-Lived Assets | Impairment of Long-Lived Assets The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. If indicators of impairment exist, an impairment loss would be recognized when the estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. The impairment charge is determined based upon the excess of the carrying value of the asset over its estimated fair value, with estimated fair value determined based upon an estimate of discounted future cash flows or other appropriate measures of estimated fair value. As of June 30, 2018 and December 31, 2017, the Company did not have any impairment charges. |
| Warrant Liability | Warrant Liability On June 3, 2016, the Company issued warrants to purchase 1,999,999 shares of its common stock pursuant to a Securities Purchase Agreement (the “Purchase Agreement”) in connection with a private placement financing transaction (the “Private Placement”). Each warrant has an exercise price of $3.66 per share and is exercisable for five years from the date of issuance. The Company accounts for these warrants as a liability instrument measured at estimated fair value. The initial fair value of the warrants was determined using a calibration model that involved using the Black-Scholes Pricing Model ("Black-Scholes"), which requires inputs such as the risk-free interest rate, expected share price volatility, underlying price per share of the Company's common stock and remaining term of the warrants. The warrants are subject to remeasurement at each balance sheet date, using Black-Scholes, with any changes in the fair value of the outstanding warrants recognized in the condensed consolidated statements of operations. As of June 30, 2018, a warrant to purchase 1,178,782 shares of the Company’s common stock remains outstanding and unexercised. |
| Contingently Redeemable Common Stock | Contingently Redeemable Common Stock In May 2017, the Company agreed to sell 407,331 shares of its contingently redeemable common stock to the Gates Foundation in a private placement at a purchase price per share equal to $24.55 (see Note 1). Common stock with embedded redemption features that are settled at the option of the holder, are considered redeemable common stock. Redeemable common stock is considered to be temporary equity and presented in a section between liabilities and equity on the Company’s consolidated balance sheets. Subsequent adjustment of the amount presented in temporary equity is required only if the Company determines that it is probable that the instrument will become redeemable. Upon termination of the redemption features, the redeemable common stock is reclassified into equity. As of June 30, 2018, 407,331 shares of contingently redeemable common stock remain as temporary equity. |
| Recent Accounting Pronouncements | Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments- Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740), Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 . The amendments add various Securities and Exchange Commission (“SEC) paragraphs pursuant to the issuance of SEC Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“Act”) (“SAB 118”). The SEC issued SAB 118 to address concerns about reporting entities’ ability to timely comply with the accounting requirements to recognize all of the effects of the Act in the period of enactment. SAB 118 allows disclosure that timely determination of some or all of the income tax effects from the Act are incomplete by the due date of the financial statements and if possible to provide a reasonable estimate. The Company has provided a reasonable estimate in the notes to the consolidated financial statements. |
| Net Loss Per Share | Net Loss Per Share Basic net loss per common share is computed by dividing the net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share is computed by dividing the net loss by the weighted-average number of common shares and dilutive common share equivalents outstanding during the period. For purposes of this calculation, preferred stock, stock options, restricted stock units and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.
Three Months Ended June 30,
Six Months Ended June 30,
2018
2017
2018
2017
Numerator:
Net loss used to compute basic net loss per share
$
(49,969
)
$
(26,070
)
$
(97,198
)
$
(59,328
)
Less: Gain on private placement warrants
(4,684
)
(4,246
)
(2,297
)
-
Net loss used to compute diluted net loss per share
$
(54,653
)
$
(30,316
)
$
(99,495
)
$
(59,328
)
Denominator:
Weighted-average shares used to compute basic net loss per share
44,865,861
38,072,763
44,612,623
36,905,802
Add: Private placement warrant shares
825,785
1,019,516
812,994
-
Weighted-average shares used to compute diluted net loss per share
45,691,646
39,092,279
45,425,617
36,905,802
Net loss per share:
Basic
$
(1.11
)
$
(0.68
)
$
(2.18
)
$
(1.61
)
Diluted
$
(1.20
)
$
(0.78
)
$
(2.19
)
$
(1.61
) For the three-month and six-month periods ended June 30, 2018 and 2017, potentially dilutive securities outstanding have been excluded from the computations of diluted weighted-average shares outstanding because such securities have an antidilutive impact due to losses reported. The following potentially dilutive securities have been excluded from diluted net loss per share, because their effect would be antidilutive, as of June 30, 2018 and 2017:
Three Months Ended June 30,
Six Months Ended June 30,
2018
2017
2018
2017
Shares subject to options to purchase common stock
6,134,950
4,594,682
6,134,950
4,594,682
Restricted stock units
1,202,694
814,627
1,202,694
814,627
Shares subject to warrants to purchase common stock
17,514
17,514
17,514
1,231,659 |
